Well, the monitor turns black whenever a mobile phone (that is close) rings or receives a sms.
The monitor is a BenQ 24" LED BL2400PT and it does not matter what mobile phone that gets close - it reacts on all of them.
If the mobile phone is approx 1m-2m away from the monitor then it will "flicker with wavy lines" and not go black.
The guy has another (Samsung) monitor next to the BenQ one and the Samsung does not get affected by the mobile phones.
Never heard of this one before.